Should older patients be selectively referred to high-volume centers for abdominal aortic surgery?

The objective of the current study was to determine the effect of hospital volume on outcomes of abdominal aortic surgery for patients older than and younger than 65 years. In order to perform this investigation, information on all adult patients who underwent abdominal aortic surgery in Maryland from 1994 to 1996 (N = 2,987 patients) in 45 acute care hospitals was obtained. Hospitals were designated as low (< 20/year), medium (20 to 36/year), or high (> 36/year) volume according to the annual number of procedures performed. The relationship of hospital volume and mortality was determined for patients less than or greater than 65 years old. Two separate multiple logistic regression models were used to adjust for patient case-mix in each age category. Of the 2,987 patients, 2,067 (69%) were older than 65 years and 920 (31%) were younger. The crude in-hospital mortality rates according to hospital volume were 2.7% (low), 2.1% (medium), and 2.7% (high) for patients younger than 65 years old (p = .8). For patients older than 65 years, in-hospital mortality rates were 11.9% (low), 9.9% (medium), and 6.9% (high) (p = .005). After adjusting for patient case-mix in a multivariate analysis, high hospital volume was associated with a decreased risk of in-hospital mortality for patients older than 65 years (OR 0.57; 95% CI 0.37 to 0.86; p = .008) but not for patients under 65 years old. In conclusion, hospital volume was associated with decreased in-hospital mortality after abdominal aortic surgery only for patients greater than 65 years old. Because of this differential effect, targeting elderly patients for regionalization would achieve most potentially avoidable deaths for this common high-risk surgical procedure.